These studies have the aim of determining the relative contributions of genes, of factors in the hemolymph and of various organs to the process of aging in Drosophila. Polytene chromosomes in Malpighian tubules and in fat bodies of D. gibberosa will be studied for age-correlated changes in gene activity. Transplants of larval fat body from young into old adults will be used to check for humoral changes in aging. A method of screening for anti-senescence mutants involves behavior tests on the F1 progeny of mutagenized males mated to attached-X females. We hope to isolate and characterize mutations that significantly affect the duration of life in D. melanogaster.